Fluid energy mills are used to reduce the particle size of a variety of materials such as, inter alia, pigments, agricultural chemicals, carbon black, ceramics, minerals and metals, pharmaceuticals, cosmetics, precious metals, propellants, resins, toner and titanium dioxide. The particle size reduction typically occurs as a result of particle-to-particle collisions, as generally, a fluid energy mill contains no moving parts. The fluid energy mill typically comprises a hollow interior that acts as a grinding chamber where the particle collisions occur. Within the grinding chamber, a vortex is formed via the introduction of compressed gases through fluid nozzles or Micronizers® positioned in an annular configuration around the periphery of the grinding chamber. The compressed gas (e.g. air, steam, nitrogen etc.), when introduced into the grinding chamber, forms a high-speed vortex as the gases travel within the grinding chamber. The gases circle within the grinding chamber at a decreased radii until released from the grinding chamber through a gas outlet. The particles to be ground are deposited within the grinding chamber and swept up into the high-speed vortex, thereby resulting in high speed particle-on-particle collisions as well as collisions with the interior portion of the grinding chamber walls. Typically the heavier the particle, the longer its residence time within the vortex and conversely the lighter particles (i.e. those sufficiently reduced particles) move with the vortex of gas until the outlet is reached. Typically, fluid energy mills are capable of producing fine (<10 microns) and ultra fine (<5 microns) particles.
Typical nozzles in the art that have found use include DeLaval nozzles (converging-diverging nozzles) through which the grinding gases (a.k.a. compression gases) are injected into the grinding chamber. In such nozzles the grinding occurs at the boundary between the particles and the high velocity grinding gas, also referred to as the shear zone. However, these types of nozzles are disadvantageous because the pattern of the gas as it exits the nozzle results in a substantial core of the gas stream flow to be unavailable for grinding because the particles cannot penetrate the fluid flow into the core. As a result, a greater amount of energy is necessary and a greater volume of compression gas is required to grind the particulate matter to the desired particle size.
Another disadvantage, with respect to fluid energy mills typically found within the art, is that they consume a significant amount of resources including energy and grinding gas due to the particular nozzles used therein.
Thus, there is a need within the industry for a mechanism for reducing energy and compression gas consumption as well as increasing the surface area of the fluid boundary useable for grinding particulate matter.